Speed Limit

http://poj.org/problem?id=2017

 #include<stdio.h>
 int main()
 {
     int n,mile,hour;
     while(~scanf("%d",&n)&&n!=-)
     {
         int sum = ,h = ;
         while(n--)
         {
             scanf("%d%d",&mile,&hour);
             h = hour-h;
             sum += mile*h;
             h = hour;
         }
         printf("%d miles\n",sum);
     }
     return ;
 }